The setEnv function inserts or resets the environment variable name in
the current environment list. If the variable name does not exist in the
list, it is inserted with the given value. If the variable does exist,
the argument overwrite is tested; if overwrite is False, the variable is
not reset, otherwise it is reset to the given value.

Program arguments

Computation getArgs returns a list of the program's command
line arguments (not including the program name), as ByteStrings.

Unlike getArgs, this function does no Unicode
decoding of the arguments; you get the exact bytes that were passed
to the program by the OS. To interpret the arguments as text, some
Unicode decoding should be applied.